Conventionally, as an electric cable for automobile wiring, an electric cable including: a stranded conductor obtained by stranding annealed copper wires according to JIS C 3102 or annealed copper wires subjected to tin plating or the like, as a conductor; and an insulator such as vinyl chloride or crosslinked polyethylene concentrically covering the conductor, is mainly used. In recent years, with an increased number of wiring positions caused by, for example, increase of various control circuits to be loaded in an automobile, a demand for durability and long time current-carrying property at a joint or the like has further increased.
Meanwhile, a proportion of a signal current circuit for control or the like has increased in an automobile wiring circuit, and a weight of an electric cable to be used has increased.
On the other hand, from viewpoints of energy conservation and the like, reduction in weight of an automobile has been required. As a measure of the requirement, weight reduction caused by reduction in diameter of a conductor of an electric cable is required. However, reduction in diameter of a conventional conductor of an electric cable involves difficulties, because the conductor itself of an electric cable and its terminal crimp part each have low mechanical strength even though the conductor of an electric cable has a sufficient current-carrying capacity.
There is proposed an example of a conductor of an electric cable produced by using a copper alloy material, which has high strength and a small wire diameter (see, for example, the Patent Document 1). Further, there is proposed an example of a conductor of an electric cable produced by stranding a plurality of copper alloy wire(s) and hard drawn copper wire(s), which has excellent mechanical and electrical properties but hardly coils (see, for example, the Patent Document 2). However, for the electric cable, required properties have become tough with improved performance of an automobile, and bending resistance is required, in particular. The electric cable is required not to break even after flexing 1,000,000 times, for example, and the conventional electric cables are not capable of satisfying such requirements.                [Patent Document 1] JP-A-6-60722 (“JP-A” means unexamined published Japanese patent application)        [Patent Document 2] JP-A-11-224538        